You won't believe, Home brew motor bogie.

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Bufferstop
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You won't believe, Home brew motor bogie.

Postby Bufferstop » Sun Jan 05, 2020 6:43 pm

You won't believe how much fiddling, tweaking, going back to the start and doing it all again it's taken over the last 12 months to get this:
John's home brew motor bogie

I set out about a year ago to build a motor bogie to make use of one of the N20 format motors coming from China along with gears from the sets of nylon gears of which Ebay has a mind bogling array. I started with a Hornby coach bogie and cut away almost everything inside the frame. Then designed and 3D printed a central block to hold the motor and a drive shaft. As the N20 motor had a very low output speed I was able to fit a large gear which drives a cog on the drive shaft mounted below it, There's a small cog on each end of the drive shaft engaging on a crown wheel mounted on each axle, one on the left one on the right to ensure they both turn the same way. Pickup is two phosphor bronze wires bearing on the wheel backs, held in place just by melting them into the 3D printed motor block.
It took many trial and error sessions to get the right combination of gears but the mixed size packs that they sell gave me a good selection to play with. Hauling power seems to depend on the weight bearing on it, but it seems happy enough pulling a couple of Hornby coaches around which is what I set out to do. My next step will be to 3D print some bogie side frames and swap the Hornby pinpoint axles for some 2mm brass rod running in top hat bearings, I doubt the pin points will last very long as driven axles.
Any how here's a picture of the underside so you can see how the drive shaft is arranged.
20180330_141321.jpg
.
And it's back to the drawing board, well mouse and screen, to fabricate a bogie designed to have a mounting boss at the top and somewhere to attach a coupler.
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Mountain
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Re: You won't believe

Postby Mountain » Sun Jan 05, 2020 8:14 pm

Very good. That looks great. The motor looks missing?

Bigmet
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Re: You won't believe

Postby Bigmet » Sun Jan 05, 2020 9:59 pm

Neat work. A good application would be EMU's with their distributed multiple traction motor bogies. That way you don't need much weight on each bogie, and the pinpoint bearings will be fine. (Stay below 100g bearing on each axle.)

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Bufferstop
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Re: You won't believe

Postby Bufferstop » Sun Jan 05, 2020 11:39 pm

Mountain - I'll get a picture showing the motor, and a motor as it comes. They are incredibly small,and have a multi stage gearbox mounted on the end of them. There's not much of it visible with the business end inside that white mounting block. You are most likely to come across them inside power operated door mirrors on cars. There are other versions which have a long screw thread as an output shaft driving a nut back and forth along the thread. Scope for larger scale point motors or animations.
Here's a motor on Ebay
n20.jpg
n20.jpg (55.96 KiB) Viewed 362 times

I'll get a photo of the one in the bogie tomorrow.
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Bufferstop
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Re: You won't believe

Postby Bufferstop » Mon Jan 06, 2020 1:07 pm

Here's three more piccies showing what's going on.
20191202_170752.jpg

The "cap" has two prongs which go inside the two pockets and slightly squeeze the sides inward to grip the motor.
20200106_122456.jpg

this is the "back end" where the brush leads go in. The big open space in the frame was to allow for height adjustment whilst I tried different gear combinations. The motor sitting on packing pieces of plasticard.
20200106_122512.jpg

This is the business end with the final gear choice fitted. It doesn't have to be 3D printed you could fabricate the same thing in plasticard (or brass!), but the joy of the 3D print is once the ideal height of the motor is worked out, it's just a few minutes work to change the computer model and a fully fitting version can be printed out.
Amazon has the motors listed now and is the first place to see if there's one for your task but probably the last place to buy one.
N20 motors at Amazon
You can find the same items on Ebay, search for "N20 Gear Motor 12 volt" or you'll be there all day. Delivery varies but I've never waited more than 10 days.
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heda
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Re: You won't believe

Postby heda » Mon Jan 06, 2020 3:14 pm

Very interesting, I've got an 0-4-0 sitting on my 'work in progress' shelf that I'm planning to gear down to use as a slow speed shunter. If I can fit one of the geared motors to give a top scale speed of say 10 mph it would be ideal.
Dave

heda
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Re: You won't believe

Postby heda » Mon Jan 06, 2020 3:28 pm

Could you measure the length of the motor and gearbox please, I intend to use it to replace a Johnson motor. It might be to slow going down from 20,000 rpm to 2,000 rpm but worth trying as there so cheap..
Dave

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Bufferstop
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Re: You won't believe

Postby Bufferstop » Mon Jan 06, 2020 10:00 pm

Heda - I'll measure the spare one I have, but I'm pretty sure it will go in the space of a Johnson. Fitting a worm is a bit problematical, it's a 3mm shaft with a flat, it's why I went for pinion and crown wheel arrangement. If you can move the whole motor backwards at a low angle you might fit a 3mm - 2mm reducer with a worm fitted to it, but some support for the other end of the shaft might be needed. If you use a worm with them you'll want one of the higher rev outputs otherwise it's too darned slow.

PS if you look on the eBay sites there's usually extra pictures one of which has the dimensions on it.
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muggins
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Re: You won't believe

Postby muggins » Tue Jan 07, 2020 7:00 am

How are those gears retained on the shafts?

heda
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Re: You won't believe

Postby heda » Tue Jan 07, 2020 10:16 am

Thanks Bufferstop, I've managed to find the size and it's near enough the same as a Johnson motor so fitting should be OK. Gearing will be another issue but something I can play with. I'll post when (if) I get it to work.
Dave

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Bufferstop
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Re: You won't believe

Postby Bufferstop » Tue Jan 07, 2020 10:59 am

Hi muggins, they are an interference fit, there's enough give in the nylon to help them slide on and stay put. If you are into heavy loads you need to look at brass gears with grubscrews. I've used them on various mechanisms and for locos pulling four or five coaches, slipping on the shaft isn't a problem.
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muggins
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Re: You won't believe

Postby muggins » Tue Jan 07, 2020 2:55 pm

Bufferstop wrote:Hi muggins, they are an interference fit


Thanks BUfferstop. I couldn't see what else it could be, but you never know ...

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Mountain
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Re: You won't believe, Home brew motor bogie.

Postby Mountain » Tue Jan 07, 2020 7:01 pm

Very nice. You have done well.

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Bufferstop
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Re: You won't believe, Home brew motor bogie.

Postby Bufferstop » Tue Jan 07, 2020 11:49 pm

Thanks Mountain, a motor stuck into a Hornby bogie doesn't sound or look like much, but you soon learn respect for the people who design them for mass production. I have an attempt at something on the design of the ringfield bogie, using a 1" diameter CD draw motor, but fitting the multi stage gear reduction into the space but with half a dozen meshings to get right, it calls for some precise dimensions. Too many years of "doing it in software" have taken the edge off my skills with the calipers.
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